188 Edible Mollusca of the Oregon Coast 
others. In 1919 the clam could still be obtained there but in 
fewer numbers than in former years. It may, however, regain its 
previous abundance as it is not much sought after and rarely 
disturbed. The species occurs in other localities both north and 
south of Yaquina Bay but its economic value as human food on 
the northwest coast may be considered almost negligible. 
8. Pholadidea penita (Conrad ).* 
Distributed northward and southward on the Oregon coast 
from Nye Beach as the locality of greatest abundance is the rock 
borer, locally known as the “rock oyster,” a bivalve mollusc of 
recognized food value. The sloping ledges of soft rock paral- 
leling the shore line just off Nye Beach abound with this species. 
They can be reached during a moderately low tide and with an 
extremely low tide large areas are exposed. The species is taken 
at other points along the Oregon coast both north and south of 
this locality, but 1s nowhere else so easily accessible or obtained 
in such abundance. The molluse is used as food quite extensively 
locally, especially during the summer months when many people 
visit this beach. Whether the species is being depleted or not 
cannot be ascertained at this time. Naturally great destruction of 
young and immature individuals occurs during the process of 
breaking the larger specimens out of the rocks. The inshore 
ledges of rock also seem to be quite well worked over but unti! 
more is known of the life history and rate of growth of the spe- 
cies nothing definitely can be asserted as to its stability or deple- 
tion. 
g. Mytilus edulis Linnaeus. 
This smaller and smoother of the two common sea mussels 
occurs along the entire Oregon coast wherever conditions will 
support it. It 1s not only found along the open ocean from 
Tillamook Head southward but is common in protected bays and 
frequently finds its way up rivers several miles from the ocean 
+ The Oregon coast is also withtn the range of a closely related species, Pholadidea 
ovoidea (Gould). A very large rock borer, probably Parapholas californica (Conrad), has 
been taken by the writer on the north shore of Yaquina Bay. It is a negligible factor, 
however, even in local food consumption, due to its scarcity. 
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